Kruger Park, which runs along South Africa’s border with Mozambique, is considered a national treasure.Kruger is a wilderness of scrub—“the bush” locals call it–where zebras and giraffes casually wander along the roads, graceful buck impalas compete for herds of does, and young hippos play-fight in shallow lakes.It is one of those rare places on earth where the humans are the ones in cages, confined to cars and campgrounds encircled by electric fences.Tourists come to seek “The Big Five”:buffalo, rhinoceros, lions, leopards, and elephants.But the ecosystem is so rich with wildlife that my family soon joked that we had come to see the Arborico Nineteen.During our half week in the area, our list grew by the day:kudu, hyena, waterbuck, wildebeest, warthog . . . .

The animals of the bush, even the huge lumbering ones, have an extraordinary ability to melt away behind the tall grasses and shrubs and scattered trees.They wander just twenty meters from the road, and you’d never know they were there—except for the elephants.That’s not because elephants can’t hide.You’d be amazed at how an elephant can vanish behind a few bushes.The reason the elephants are ever-present, even in their absence, is because they are so destructive.

Elephants strip the bark off of trees.They push other trees over so that they can eat the leaves, fruit and new growth. In both cases, if they are thorough, the trees die. I’m not talking about saplings.On a “walking safari” led by an armed park ranger, I pointed to a tree that maybe, maybe, Brian and I together could wrap our arms around together.“Could an elephant push that one over?” I asked.

“Absolutely,” was the answer.A fellow traveler said he had seen a giant baobab taken apart by an elephant:by the end, it looked like someone had finished the job with a wood chipper.Tree destruction is a natural behavior for elephants and a part of nature’s balance—except when it isn’t.The problem is that they push trees over not only when they are feeling hungry, but also when they are feeling stressed, or crowded or sometimes just plain ornery.When an elephant needs elbow room, a tree can feel intrusive.And so the park has a problem.

In the last fifteen years, the elephant population of Kruger has risen to 15,000.It is now more or less double what biologists estimated to be the sustainable carrying capacity.In a world with fewer humans, the elephants would migrate onto grasslands following a seasonal cycle that would allow treed areas to recover from the damage done during the months they passed through.In a world with fenced park boundaries, the elephants may be turning the bush into grasslands.

What’s to be done?Until the mid 1990’s rangers culled the elephant herds.Elephants are so smart and attached to each other that they had to kill a whole family unit at once.The goal was to isolate the herd and then kill them all within five minutes.Any who escaped the slaughter would be distraught and dangerous.The process was efficient, and the meat was salvaged, but still, no one could deny it involved the slaughter of highly intelligent beings who knew exactly what was going on, and animal rights groups brought it to an end.Private game reserves that bound Kruger on the west are experimenting with elephant contraception.An annual injection thickens the lining around the egg so that elephant sperm can’t penetrate.Gamekeepers who have committed to no killing are optimistic.But the process is costly, too costly for the national park.It requires helicopters and the ability to track which elephants have received the contraceptive—fine when you have a herd or two; impossible for 15,000 elephants on 20,000 square kilometers.

Of course, the real issue isn’t an overabundance of elephants, it’s an overabundance of humans.It isn’tthe trees that are being killed in the park, but the bush that has been clear-cut outside the park for citrus orchards and sugar cane and cattle ranches and towns.It isn’t the grey animals that huddle in herd of five to fifty but the pink and brown animals that huddle in herds of five to fifty million and that are willing to knock down everything in their path when they are hungry or need elbow room.

South Africa’s population is 20,000 elephants and 49,000,000 humans, with the human population growing by 500,000 a year.(Without AIDS, the growth rate would be almost double.)Karen Kingsolver, in her novel, The Poisonwood Bible, put it this way, “When Albert Schweitzer walked into the jungle, bless his heart, he carried antibacterials and a potent, altogether new conviction that no one should die young.He meant to save every child, thinking Africa would then learn to have fewer children.But when families have spent a million years making nine in the hope of saving one, they cannot stop making nine.Culture is a slingshot moved by the force of the past.”

The challenge of overpopulation is one that turns moral certainties on their heads.It leaves whole societies party to an anxious quandary in which people of good will fight each other, sometimes to the death, over contraception and abortion and immigration and all manner of charities and policies that ease human suffering at the expense of future generations and other species.Throughout human history, more has always been better—more tree cutting, more harvesting, more people.But now, having outsmarted nature, we are left with rutted wastelands stretching the width of continents.The price of our longevity and fertility is hunger and war and the extermination of life forms ranging from frogs to rhinos and possibly, in the long run, ourselves.

From the vantage of an exhausted mother arriving at a clinic door after walking barefoot through the night with a toddler tied to her back, Schweitzer’s antibacterials were a gift more precious than any other, the gift of life to a dying child.Better yet is vaccination, which may be humanity’s greatest triumph in the service of compassion.I praise science, sometimes daily, that I’ve never had to wonder whether my cherished daughters were going to die of polio or smallpox or rubella or tetanus or, here in Africa, of cholera or dysentery.And yet, from the vantage of any species other than humans, antibiotics and vaccinations may be this planet’s biggest catastrophe.

Human culture is not the only slingshot moved by the force of the past.Biology is another.Our inability to deal with population may be encoded in our very bodies, in the moral instincts born of our ancestral environment that make life precious in some absolute sense and human life precious to the point that we create deities in our own image.When our ancestors walked upright out of the Great Rift Valley, when they made their way across the European continent, braving ever harsher winters, it took all the libido they could muster and all the effort they could call out of their hungry bodies to keep the next generation alive.Life and death hung in tenuous balance.

From those beginnings, instinctively, we believe that human life—more of it, longer, right here, right now, no matter what the cost–is the highest good.We fight death with tooth and nail and vaccine and antibiotic and pacemaker and feeding tube.Our emotions tell us to save the babies, all of them—even fetuses and newborns with empty craniums and kittens and puppies and baby elephants and other big-eyed beneficiaries of our parental instincts.But what if the situation has changed so radically that those emotions can no longer point the way to happy healthy children and grandchildren and beyond?

What we fail to acknowledge is that all life, even our own, depends on death in a cycle that ultimately lies beyond our control.We cannot choose life over death, only some life over other life: Human life over a diverse tapestry of life perhaps; more individual lives over longer richer lives; one pregnancy over another; the life of humans present over humans future.We are like the child given the choice of the red lollypop or the green who insists that he can choose them both.

The Chinese, faced with the mathematics of exponential growth, turned the science of elephant management in its more high tech form—not culling but forced universal contraception—on themselves.Ordinary humans liked the rules about as much as the elephants like helicopters and dart guns.The West screamed, partly to make political hay out of Cold War politics, but partly out of genuine horror:The freedom to reproduce is sacred, a basic human right, mandated by a god—or several—who said, “Go forth and multiply.”

Go forth and multiply, God said to us.Go forth and multiply he said to the elephants.To make sure we listened, he built the command into our body’s pleasures, into infatuation and orgasm and the sweet pleasure of nuzzling or nursing a baby.Just outside of Kruger, by a town called Hoedspruit, lies a small endangered species center that was given a gift of two baby rhinos –one of which traveled by boat from England, sent by her owner to live on native soil.They grew big together and were transferred to a larger fenced area across the road from the clinic and cages so they would have room to move about and graze and, hopefully, multiply.One morning, they were found dead, five bullets from an AK 47 in one, two in the other, their noses stripped of the stubby horns that are prized in China for (imagined) aphrodisiac qualities.China holds a billion humans, this planet a few thousand rhinos.The murder of rhinos under the mathematical circumstances tells us the power of our drive to reproduce.

Our temptation, always, is to follow the voice of God-in-our-bodies to our doom.“Go forth and take dominion,” he said, and we enslaved the animals that could understand our commands, stacked tortoises in the holds of ships, and killed seas of buffalo to show that we could. “Go forth and sow seed,” he said, and filled with a restless dissatisfaction, by sweat and blood, we farmed the valleys of the fertile crescent and hacked rice paddies out of the hillsides and cleared the rainforests for bananas and oil palms.“Go forth and preach the Good News,” and we carried our religions and fantasies of political utopia to isolated tribes with a righteous superiority that could turn any good news into bad.“Go forth and claim your promised land,” he said.And driven by instinct and emotion we built ourselves swords and bombs, and we salted the fields with sodium and then depleted uranium, ensuring that the land was suitable for no one.“Go forth and eat,” God said, and he built it into our yearnings so that in our modern paradise of culinary bounty we eat ourselves into obesity and wastelands and death by starvation.That is because the voice of God is the voice of our ancestors, who in their million years of creating us never held in their hands a paradise of culinary bounty, or depleted uranium, or an AK-47.A million years of scarcity don’t prepare you for surplus.

What is to be done about too much of a good thing—too much of the wonder that we call an elephant or a human being?On this question, God has given us an answer we may not like, more vague and less visceral than the others:Go forth and think.The thing that distinguishes us most from our next of kin, chimpanzees and bonobos, is that the human ancestors who walked out of the Eden we now call Congo, found a brilliant way to adapt to unfamiliar situations, ones that neither they nor their ancestors had encountered before.It is called reasoning.That is what all our grey matter is for.It’s why generation after generation of those ancestors sacrificed females and babies to the physics of getting a big cranium through a small birth canal.

Emotions and instincts are for dealing with the familiar.Reason, refined into logic, mathematics, the scientific method and ethical codes–and funneled into the messy muddled mundane process of policy-making–this is the voice of god, the voice of our ancestors, the voice of the future when emotion and instinct fail.And fail they do when it comes to overpopulation.No answer is emotionally satisfying.Each has its own set of griefs and losses.Each feels uneasy and unfamiliar.It is tempting to go backwards – to return to something that feels simple and familiar:Love the babies.Love them all.Every precious embryo, every exquisite little newborn elephant.Pretend the problem isn’t there.God will solve it.

Actually he will.He is perfectly willing to deploy his old solutions:lions—conflict–AIDS–starvation.The four horsemen are lined up, waiting for the call.The question is whether, by accepting the gift and responsibility of reason, we can do better.